linux-kernel - Re: [PATCH 1/7] work_on_cpu: helper for doing task on a CPU.

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20081023094036.GA7593@redhat.com>
Date:	Thu, 23 Oct 2008 11:40:36 +0200
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	linux-kernel@...r.kernel.org, travis@....com,
	Ingo Molnar <mingo@...e.hu>, Gautham R Shenoy <ego@...ibm.com>
Subject: Re: [PATCH 1/7] work_on_cpu: helper for doing task on a CPU.

On 10/23, Rusty Russell wrote:
>
> +long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg)
> +{
> +	struct work_for_cpu wfc;
> +
> +	INIT_WORK(&wfc.work, do_work_for_cpu);
> +	init_completion(&wfc.done);
> +	wfc.fn = fn;
> +	wfc.arg = arg;
> +	get_online_cpus();
> +	if (unlikely(!cpu_online(cpu))) {
> +		wfc.ret = -EINVAL;
> +		complete(&wfc.done);
> +	} else
> +		schedule_work_on(cpu, &wfc.work);

I do not claim this is wrong, but imho the code is a bit lisleading and
needs a comment (or the "fix", please see below).

Once we drop cpu_hotplug lock, CPU can go away and this work can migrate
to another cpu.

> +	put_online_cpus();
> +	wait_for_completion(&wfc.done);

Actually you don't need work_for_cpu->done, you can use flush_work().

IOW, I'd suggest

	long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg)
	{
		struct work_for_cpu wfc;

		INIT_WORK(&wfc.work, do_work_for_cpu);
		wfc.fn = fn;
		wfc.arg = arg;
		wfc.ret = -EINVAL;

		get_online_cpus();
		if (likely(cpu_online(cpu))) {
			schedule_work_on(cpu, &wfc.work);
			flush_work(&wfc.work);
		}
		put_online_cpus();

		return wfc.ret;
	}

Oleg.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/